Natural and synthetic gases containing acidic components such as CO.sub.2, H.sub.2 S, COS, and the like, have been treated on a commercial scale with aqueous alkanolamine solutions to remove the acidic components. The severe corrosion which results from the presence of these components, particularly in the rich absorbent solution regeneration section, has necessitated keeping the concentration of the amine low, i.e., 10-30 percent generally and the loading, i.e. the amount of H.sub.2 S/CO.sub.2, in the absorbent solution, low. In light of the recent energy shortage and necessity to conserve energy it would be advantageous to more heavily load the gas treating solutions with the acidic components. It would be a further advantage to employ more concentrated absorbent solutions. However to accomplish these objects it is necessary to prevent any increase in corrosion and it would be more advantageous to reduce the corrosion to less than that experienced today at the lower loadings and solution concentrations.
A brief review of the prior art discloses that numerous patents have taught various polyamines as corrosion inhibitors for various fluids:
For example, Dickson et al. in U.S. Pat. No. 3,262,791, which is representative of many patents in the corrosion inhibitor field issued to Petrolite Corporation, describes polyalkylenimines of molecular weight above 800 as useful in preventing corrosion of iron, steel and ferrous alloys when using slushing oils. The patent also suggests these polyalkylenimines as capable of imparting corrosion resistance to brines, weak inorganic acids, organic acids, CO.sub.2, H.sub.2 S, etc.
Ting Sin Go in U.S. Pat. No. 3,819,328, also a Petrolite patent, discloses alkylene polyamines, such as ethylene diamine, to control acid corrosion in distillation columns, such as occurs in petroleum distillation columns. Preferably the alkylene polyamine is used in conjunction with a corrosion inhibitor, e.g., a film-forming corrosion inhibitor, i.e., morpholine, at regulated pH's of about 2. The corrosion of columns which have water condensers and which water has a high pH due to acidic materials such as H.sub.2 S, HCN, CO.sub.2, HCl, etc. is taught to be controlled.
Ulrich et al. in U.S. Pat. No. 2,143,393 discloses absorbing acid gases in an aqueous solution of a polymerized alkylenimine.
Johnson et al. in U.S. Pat. No. 3,137,654 teach using glycines as a corrosion inhibitor in an alkanolamine solution used to absorb CO.sub.2 from industrial gases.
Yeakey et al. in U.S. Pat. No. 3,829,494 teach using a water-soluble trialkanolamine in an aqueous 2-(2-aminoethoxy)ethanol gas scrubbing medium.
Singh in U.S. Pat. No. 3,535,260 teaches a similar result for monoethanolamine gas treating solutions.
The art is rife with disclosures of nitrogen containing compounds useful as corrosion inhibitors, but that only a few are commercially acceptable. It is evident to one skilled in the art operating a commercial installation that the old limitations on concentration of absorbent, loading of the absorbent solution, etc., while improved to some extent with these few commercially accepted inhibitors are lacking in ability to carry without excessive corrosion the demands for more efficient operation, higher absorbent concentrations and higher loading, brought on by the energy shortage.
Is is therefore an object of the present invention to provide an inhibitor for aqueous amine gas absorbing systems which will enable higher concentrations of the amine absorbent to be used as well as a higher loading of the acid gases in the absorbent with reduced corrosion.
These and other advantages of the present invention will be apparent to those skilled in the art from the following disclosure and claims.